为获取在役混凝土T梁疲劳刚度退化规律，开展疲劳寿命预测，基于损伤力学理论构建了考虑开裂损伤的混凝土T梁阶梯刚度模型，通过对3根10 m钢筋混凝土T梁足尺模型进行静力和疲劳破坏试验，获取了疲劳剩余刚度随荷载作用次数的演化规律。引入疲劳损伤系数和刚度退化系数，建立了在役混凝土T梁疲劳寿命预测模型。分析结果表明：随着荷载作用次数的增加，桥梁剩余刚度呈现三阶段衰减，其中疲劳初期和后期阶段衰减较快，但占总寿命比重相对较小，而疲劳中期阶段呈线性稳定退化，约占疲劳总寿命的80%以上，为桥梁服役的主要阶段，疲劳破坏时剩余刚度约为初始刚度的82.7%。最终，针对在役混凝土T梁桥工作性状，提出了在役钢筋混凝土梁桥寿命预测方法，相关研究成果可为此类桥梁寿命预测研究提供理论支持。

In order to obtain the fatigue stiffness degradation law of in-service concrete T-beams and carry out fatigue life prediction. Based on the theory of damage mechanics， a stepped stiffness model of concrete T-beams including cracking damage was constructed. Through the full-scale model of three 10 m concrete T beams， static and fatigue failure tests were carried out to obtain the evolution law of fatigue residual stiffness with the number of loads. The fatigue damage coefficient and stiffness degradation coefficient were introduced to establish a concrete T beam in service fatigue life prediction model. The analysis results show that with the increase of load， the residual stiffness of the bridge exhibits three-stage decay， in which the initial and later stages of fatigue decay rapidly， but account for a relatively small proportion of the whole life. The result shows that more than 80% of the whole service life is the main stage of bridge service， it is about 82.7% of the initial stiffness at the time of fatigue failure. Finally， according to the working behavior of in-service concrete T-girder bridges， a life prediction method for in-service reinforced concrete girder bridges is proposed， the related research results can provide theoretical support for the study of life prediction of such bridges.